1. Field of the Invention
The present invention is generally related to the area of lights and more particularly relates to techniques for generating daylight-like light from green laser and magenta phosphor. Such light is used in headlights of automobiles in one embodiment.
2. Description of the Related Art
Laser is produced from a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The term “laser” originated as an acronym for “light amplification by stimulated emission of radiation”. Lasers differ from other sources of light because they emit light coherently. Spatial coherence allows a laser to be focused to a spot, enabling applications like laser cutting and lithography. Spatial coherence also allows a laser beam to stay narrow over long distances (collimation), enabling applications such as laser pointers. Lasers can also have high temporal coherence which allows them to have a very narrow spectrum, namely, they only emit a single color of light.
Lasers have many important applications. They are used in common consumer devices such as DVD players, laser printers, and barcode scanners. They are used in medicine for laser surgery and various skin treatments, and in industry for cutting and welding materials. They are also used in military and law enforcement devices for marking targets and measuring range and speed.
Recently BMW and Audi feature laser headlights in their certain models. The laser headlights are said to be 30 percent more energy efficient than the basic LED headlights, and to reduce bulk and weight by replacing the standard LEDs with laser diodes that are 10 times smaller. Further, it reports that the light of a laser headlamp is extremely bright, similar to daylight, which is perceived by the human eye as pleasant.
Similar to the daylight, the light of a laser headlamp shall be in white or substantially white color. To produce white color laser, one or more blue lasers are used and focused into a lens filled with yellow phosphorus. The yellow phosphorus, when excited by the blue laser, emits an intense white light. As further described below, blue lasers are not efficient. In fact, the blue laser is the lowest in light intensity when perceived by the human eyes.
Accordingly, there is a need for even more efficient laser that can be used to generate white laser. Such white laser may be used in laser headlights for vehicles, laser video or movie projection and other illumination applications.
Lasers differ from other sources of light because they emit light coherently. Spatial coherence allows a laser to stay narrow over long distances (collimation). When two vehicles are on road, there is a need for brief communication between the two vehicles. The laser-base light makes the communication between two vehicles possible by projecting a predefined light pattern from one vehicle to another. The received light pattern delivers a specific message according to a predefined protocol or based on a common understanding.
The predefined light pattern is formed by a light controller operating on a LCD or LCoS unit that can be programmed or electronically controlled in accordance with a command from a driver or a camera monitoring a surrounding of a vehicle.
There is a further need to prevent from projecting light onto a rear view window of a vehicle ahead to cause reflection from the rear-view mirror so as to interfere with the driver of the vehicle.